Location determination systems can estimate a location of a device using various techniques. For example, some location determination systems use time-of-flight measurements of WiFi-capable devices to estimate a distance of a device from a wireless access point. If there are time-of-flight measurements available from multiple access points, a technique such as multilateration may be used to estimate the location of the device. Time-of-flight-based location determination systems have the advantage of being able to determine the location of a device in an indoor environment, where GPS signals may be blocked, for example, Improving the accuracy of location determination systems may be advantageous to provide more actionable data, such as for targeted advertisements in a retail store or mall.